Ambient air backflushed filter vacuum

ABSTRACT

A vacuum cleaning machine has a cannister with an inlet port and at least two outlet ports. At least two filters are disposed inside of the cannister, one in pneumatic communication through each of the outlet ports. At least two valves are disposed outside of the cannister. Each valve is in pneumatic communication between a vacuum source and an outlet port so as to permit air to be drawn by the vacuum source from the inlet port simultaneously through the filters. A controller operates the valves to switch the filters from the vacuum source to ambient air so as to permit ambient air to be sequentially intermittently drawn through corresponding valves and filters into the cannister. Preferably, the controller includes a timing mechanism for setting the delay time of the sequential valve operation and a timing mechanism for setting the intermittent time of connection of each filter to ambient air.

BACKGROUND OF THE INVENTION

This invention relates generally to vacuum cleaning equipment and moreparticularly concerns a vacuum cleaner having filters backflushed withambient air.

Cleaning filtered vacuums is presently accomplished by shaker,percussion, forced air or compressed air systems. Such systemsperiodically apply mechanical or pneumatic forces to dislodge particlescollected on the intake surfaces of the filters. To accomplish this, aforce system other than the primary vacuum system is required, such as asecond blower motor, a compressor or a shaker or percussion systemmotor. These added components make backflushed vacuums considerably moreexpensive and more readily subject to malfunction.

Except for very expensive complex 240 volt systems, these systems aremechanically controlled. Therefore, they have limited flexibility intheir operating parameters. While their cycle time can be varied,perhaps by changing the rotational speed of a cam, the fractionalrelationship of the backflush time to full cycle time can only bechanged by an exchange of mechanical components, such as the cam drivemotor. The efficiency of the backflush cycle, however, is dependent onthe proper coordination of the cycle and backflush times to thecharacteristics of the particular medium being vacuumed. For example, ashort burst of backflushed air will clean dust collected on a filter,but a longer burst is necessary to dislodge particles of plastic orfibers.

These problems are exacerbated because these systems generally exhibitconsiderable turbulence within the collecting cannister, and as a resultthe same particles are often continuously recycled, unnecessarilyoverloading the backflush system.

It is, therefore, an object of this invention to provide a backflushedfilter vacuum which uses ambient air to backflush the filters. Anotherobject of this invention is to provide a backflushed filter vacuum whichdoes not require use of a secondary shaker, percussion, forced air orcompressed air system. A further object of this invention is to providea backflushed filter vacuum which can be controlled by an electronicsystem economically compatible with a relatively inexpensive 120 voltmachine. Yet another object of this invention is to provide abackflushed filter vacuum which permits independent control of bothcycle and backflush time. It is also an object of this invention toprovide a backflushed filter vacuum which permits cycle and backflushtimes to be varied relative to each other without interchangingmechanical components. Still another object of this invention is toprovide a backflushed filter vacuum which permits the user to adjustcycle and backflush times to suit the medium being vacuumed. Anadditional object of this invention is to provide a backflushed filtervacuum which reduces the likelihood of recycling particles through thefilters.

SUMMARY OF THE INVENTION

In accordance with the invention, a vacuum cleaning machine has acannister with an inlet port and at least two outlet ports. At least twofilters are disposed inside of the cannister, one in pneumaticcommunication through a corresponding one of each of the outlet ports.At least two valves are disposed outside of the cannister. Each valve isin pneumatic communication between a vacuum source and a correspondingoutlet port so as to permit air to be drawn by the vacuum source fromthe inlet port simultaneously through the filters. A controller operatesthe valves to switch the filters from connection to the vacuum source toconnection to ambient air so as to permit ambient air to be sequentiallyintermittently drawn through corresponding valves and filters into thecannister. Preferably, the controller includes a timing mechanism forsetting the delay time between cycles of the sequential valve operationand a timing mechanism for setting the intermittent time of connectionof each filter to ambient air.

The preferred valve has a housing with a continuously opened port andtwo reciprocally opened and closed ports. A piston disposed between thetwo ports is biased to a first position in which one of the two ports isclosed and the other of the two ports is opened. A mechanism forovercoming the bias moves the piston to a second position in which theclosed port is opened and the opened port is closed. The preferred biasovercoming mechanism is a solenoid with a switch. The continuouslyopened port is in pneumatic communication with the filter. One of thetwo reciprocal ports is in pneumatic communication with the vacuumsource and the other with ambient air. When the solenoid is energized,the valve connects its filter to ambient air. When the solenoid isde-energized, the valve connects its filter to the vacuum source.

In a specially preferred embodiment, the vacuum cleaning machine has acannister with an opening in its top and an inlet port. A plate closesthe opening. The plate has three outlet ports. Three filters are mountedon the plate and disposed inside of the cannister, one in pneumaticcommunication through a corresponding one of each of the outlet ports. Avacuum source and three valves are also mounted on the plate outside ofthe cannister. Each valve has a first port in continuously openedpneumatic communication with a corresponding outlet port, a second portin pneumatic communication with the vacuum source and a third port inpneumatic communication with a source of ambient air. A pistonreciprocally disposed between the second and third ports is biased by acoil spring to simultaneously close the third port and open the secondport in a vacuum mode. A solenoid overcoming the bias reciprocates thepiston to simultaneously close the second port and open the third portin a backflush mode. The controller causes the valves to sequentiallyswitch the filters from communication with the vacuum source tocommunication with ambient air for a preset time. The controller ispreferably configured to allow the operator to set the cycle time of thesequential valve operation and also to set the intermittent time ofconnection of the filters to ambient air.

Preferably, the cannister also contains a mechanism cooperable with theinlet port to divide the cannister into an upper zone of high velocityvortex air flow and a lower zone of reduced velocity air flow so as toreduce the likelihood of recycling particles through the filters. Thiscan be achieved by positioning the inlet port below the filters andabove the bottom of the cannister using a duct to redirect air flowdownwardly in the cannister from the inlet port and using a baffle toredirect the downward flow to a circumferential flow.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings in which:

FIG. 1 is a block diagram of the ambient air backflushed filter vacuum;

FIG. 2 is a side elevation of the ambient air backflushed filter vacuum;

FIG. 3 is a top plan view of the backflushed filter vacuum pneumatics;

FIG. 4 is a top plan view of a typical valve of the backflushed filtervacuum;

FIG. 5 is a side elevation view of the valve of FIG. 4;

FIG. 6 is a plan view of an electro-mechanical control system for thebackflushed filter vacuum valves;

FIG. 7 is a schematic electrical diagram of the electro-mechanicalsystem of FIG. 6;

FIG. 8 is a block diagram of an electronic control system for thebackflushed filter vacuum valves; and

FIG. 9 is a schematic diagram of the electronic control system of FIG.8.

While the invention will be described in connection with a preferredembodiment, it will be understood that it is not intended to limit theinvention to that embodiment. On the contrary, it is intended to coverall alternatives, modifications and equivalents as may be includedwithin the spirit and scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION

Turning first to FIG. 1, the ambient air backflushed filter vacuumgenerally includes a cannister 10 with three, outlet ports 11, 12 and 13and an inlet port 14. Three filters 21, 22 and 23 are disposed withinthe cannister 10 and three valves 31, 32 and 33 are disposed outside ofthe cannister 10. Each of the valves 31, 32 and 33 has a continuouslyopened port 31 c, 32 c or 33 c which is in constant communicationthrough a respective outlet port 11, 12 or 13 with a respective filter21, 22 or 23. Each valve 31, 32 and 33 also has two reciprocally openedand closed ports 31 a and 31 b, 32 a and 32 b and 33 a and 33 b,respectively, and an operating mechanism 31 d, 32 d and 33 d,respectively, for switching the valves 31, 32 and 33 between theirreciprocal ports “a” and “b”. One reciprocal port “a” of each of thevalves 31, 32 and 33 is connected to a vaccum source 15 and the otherreciprocal port “b” of each of the valves 31, 32 and 33 is in pneumaticcommunication with a source of ambient air 16. A controller 17 causesthe operating mechanisms 31 d, 32 d and 33 d to sequentially operate toswitch the filters 21, 22 and 23 from pneumatic communication with thevacuum source 15 to pneumatic communication with ambient air 16. Each ofthe valves 31, 32 and 33 is normally connected so that the vacuum source15 draws ambient air 16 through the cannister inlet port 14 into thecannister 10 and through the walls of the filters 21, 22 and 23. Thecontroller 17 then sequentially causes the valves 31, 32 and 33 toswitch to the ambient air port “b”. When, for example, one valve 31 isin this backflushed mode through its ambient air port “b”, the othervalves 32 and 33 continue in the vacuum mode through their respectivevacuum ports “a”. The suction through the filters 22 and 23 drawsambient air 16 through the valve port 31 “b” and into the filter 21,reversing the flow of air through the filter 21 and causing particlesthat have collected on the outer wall of filter 21 to be dislodged todrop to the bottom of the cannister 10. After a brief, predeterminedbackflush time, the controller 17 will cause the first valve 31 toreturn to its vacuum port “a” so as to resume the vacuum mode throughall three filters 21, 22 and 23. After another predetermined time lapse,the controller 17 will sequentially perform the same operation on asecond valve 32, so that the other valves 31 and 33 cause the secondfilter 22 to be backflushed. When the second filter 22 has beenbackflushed for the predetermined time period and the delay time haselapsed, the controller 17 will then cause the same operation to occurwith respect to the third filter 23. The cycle continues for as long asthe vacuum source 15 is in operation. When the third filter 23 has beenbackflushed, the controller 17 will delay for a predetermined timeperiod before reinitiating the cycle. Preferably, and as hereinafterexplained, the controller 17 is configured so as to allow the user toselect both the delay time and the backflush time for the system.

Turning now to FIG. 2, the structural configuration of the cannister 10is illustrated. The cannister 10 is a cylindrical container having sidewalls 18, a bottom 24 and an open top. The open top is covered by acircular plate 19. The filters 21, 22 and 23 are mounted to the bottomof the plate 19 and pneumatically communicate through the outlet ports11, 12 and 13 in the plate 19. The inlet port 14 to the cannister 10extends through its side wall 18, as shown at a point below the bottomof the filters 21, 22 and 23 and above the bottom 24 of the cannister.The valves 31, 32 and 33, the operating mechanisms 31 d, 32 d and 33 d,the controller 17 and the vacuum source 15 are mounted above the plate19 and are protected by a cover 25 which is seated on the plate 19. Anopening 26 is provided in the cover 25 to exhaust air discharged fromthe vacuum source 15. A handle 27 is provided proximate the bottom ofthe cannister 10 to facilitate lifting and handling of the unit. Casters28 at the bottom 24 of the cannister 10 allow the cannister 10 to befreely rolled in any direction. Latches 29 permit removal of the cover25 and the plate 19 from the cannister 10 to allow access to theinterior of the cannister 10 and the filters 21, 22 and 23.

Continuing to look at FIG. 2, an assembly for maximizing the efficiencyof airflow within the cannister 10 during use is also seen. A duct 41 isprovided inside the cannister 10 to redirect air flow through the inletport 14 downwardly and proximate the side wall 18 of the cannister 10.The inlet port 14 can be above the bottom level of the filters 21, 22and 23 as long as the duct 41 extends below the filters 21, 22 and 23. Abaffle 42 is positioned within the cannister 10 slightly below theoutlet end of the duct 41. The baffle 42 is sized to provide a barrierto the path of air flow from the duct 41. As shown, the baffle 42 issecured to the cannister wall 18 by an external bolt 43 which can beloosened to permit changing the angle of inclination of the baffle 42from horizontal. The baffle 42 redirects the air flow into a circularvortex above the baffle 42. Below the baffle 42, air flow velocities areconsiderably reduced and there is little turbulence. As a result, whenparticles filtered by the filters 21, 22 and 23 are backflushed from thefilters 21, 22 and 23, the particles settle to the bottom 24 of thecannister 10 and are far less likely to be recycled through the filters21, 22 and 23. It has been found that a baffle angle of 10 degrees fromhorizontal works effectively, though this angle may be variedconsiderably.

Turning now to FIG. 3, a preferred embodiment of the valves 31, 32 and33 and their operating mechanisms is illustrated. A central housing 44is preferably concentrically located on top of the circular plate 19covering the cannister 10. The central housing 44 may be fixed to theplate 19 by screws 45 and a plate 46 covering the central housing 44 isalso fastened to the housing 44 by screws 47. A concentric motor mountspacer 48 is fastened to the top of the central housing cover plate 46and extends upwardly to and supports the mount 49 for the vacuum source15. The valves 31, 32 and 33 are concentrically disposed about thecentral housing 44, preferably displaced at equal angles. Thus, asshown, for the three valve configuration, the valves 31, 32 and 33 areat 120 degree intervals about the center of the central housing 44.

The configuration of each of the valves 31, 32 and 33 is shown in FIGS.4 and 5 and is explained in relation to one of the valves 31. The othervalves 32 and 33 are in all respects identical to the valve 31 nowdescribed. A mounting plate 51 is fixed to the cannister plate 19 at anelevation determined by standoffs 52. The valve 31 is formed by acylindrical housing 34 also fastened to the cannister plate 19 byscrews. The central housing 46 is connected to the valve housing 34 by aradial duct 45. The ambient air port 31 b is radially aligned with theduct 35 which forms the vacuum port 31 a for the valve 31. The ambientair duct 36 extends from the ambient air port 31 b into the source ofambient air 16. The valve housing 34 is completed by a cover 37 fastenedto the top of the housing 34 by screws 38.

The operating mechanism 31 d for the valve 31, shown generally in FIG.1, is also shown in greater detail in FIGS. 4 and 5. A solenoid 61 ismounted on a plate 51 with the solenoid shaft 62 aligned on the radiusextending through the central axis of the ducts 35 and 36. The remainderof the operating mechanism 31 d is best understood in relation to themanner in which it is assembled. The solenoid shaft 62 has a threadedportion on which is threaded a bolt 63. A gasket 64 and valve plate 65slide over the shaft 62 with the plate 65 against the bolt 63 and thebolt 63 seated in a hole in the gasket 64. The gasket 64 and plate 65are configured to cover the vacuum port 31 a of the valve 31. A sleeve66 slides over the shaft 62 against the valve plate 65. An integralbushing 67 and bracket 68 slide over the sleeve 66 and a spring 69slides over the sleeve 66 and against the bushing 67. A second valveplate 71 and gasket 72 slide onto the shaft 62 and against the sleeve66. A nut 73 is tightened onto the threaded end of the shaft 62 andseats in a hole in the gasket 72 against the second plate 71. The secondvalve plate 71 and gasket 72 are configured so as to cover the ambientair port 31 b of the valve 31. The valve plates 65 and 71 taken togetherform a piston of a length determined by the length of the sleeve 66. Thebracket 68 is fastened to the valve cover 37 by screws 74. The travel ofthe piston is therefore determined by the spacing of the vacuum port 31a and the ambient air port 31 b. The solenoid 61 and the spring 69 arecoordinated so the spring 69 exerts 2.3 psi against the second valveplate 71 in its preloaded condition and can be fully compressed at 4psi. The spring 69 normally holds the ambient air port 31 b closed andthe vacuum air port 31 a opened. When the solenoid 61 is energized, itspull overcomes the spring 69 to shift the piston to close the vacuumport 31 a and open the ambient air port 31 b of the valve 31.

As seen in FIG. 4, additional solenoids can be mounted at 120 degreeintervals on the solenoid mounting plate 51 to serve the remainingvalves illustrated in FIG. 3. Coordinated selection of the solenoid 61,the spring 69, the diameter of the valve housing 34 and the length ofthe piston defined by the valve plates 65 and 71 and the sleeve 66 inthe above described assembly procedure automatically establishes thepiston travel distances and preloads the appropriate spring compression.Upon energizing the solenoid 61, the bias of the spring 69 is overcomeand the solenoid 61 quickly pulls the piston to close the vacuum port 31a and open the ambient air port 31 b of the valve 31. A central opening54 in the cover plate 46 in the central housing 44 allows pneumaticcommunication through the cylindrical spacer 48 to the vacuum source 15.All of the housing and duct components are sealed at their connectionsto assure the pneumatic integrity of the system.

Turning now to FIGS. 6 and 7, an electro-mechanical embodiment of thecontroller 17 is illustrated. In this embodiment solenoids 61, 62 and 63are controlled by switches 81, 82 and 83, respectively, which areoperated by a cam 84 driven by a geared cam motor 85 connected to thecam 84 by a drive shaft 86. The cycle time for operation of the switches81, 82 and 83 by the cam 84 is not adjustable without a change ofstructural components, such as selection of a motor with a differentrpm. The components of the controller 17 are connected as illustratedthrough a terminal block 88. The vacuum source 15 and main power on/offswitch 89 are also connected via the terminal block 88. The vacuum motor15 is grounded 91 and the cam motor 85 is provided with a capacitor 92to assist in operation of the motor 85. When the machine main powerswitch 89 is turned on, the vacuum motor 15 and cam motor 85 are bothenergized. As long as the switches 81, 82 and 83 remain open, thesolenoids 61, 62 and 63 remain de-energized and all of the filters 21,22 and 23 are connected to the vacuum source 15 through the valve vacuumports 31 a, 32 a and 33 a. As the cam 84 rotates to engage the next ofthe switches 81, 82 or 83 in its path, the solenoids 61, 62 and 63 aresequentially energized to close their respective vacuum ports 31 a, 32 aand 33 a and to open their ambient air ports 31 b, 32 b or 33 b,respectively, so as to connect their respective filters 21, 22 or 23 toambient air 16. The filter 21, 22 or 23 will be backflushed for as longas their associated solenoids 61, 62 or 63 remain energized, a perioddetermined by the relation of the cam 64 to the contact elements of theswitches 81, 82 or 83. As shown in FIG. 6, the controller 17 and itscomponents are mounted on the cannister plate 19.

Turning now to FIGS. 8 and 9, an electronic embodiment of the controller17 is illustrated. In this embodiment, when the system main power switchis turned on, the controller power switch 101 is also turned on. Thecontroller consists essentially of two timers 102 and 103. The firsttimer 102 establishes the delay time between activation of the solenoids61, 62 and 63. The second timer 103 establishes the “on” time for eachof the solenoids 61, 62 and 63 and an “off” time before the nextsolenoid 61, 62 or 63 is energized. The use of this embodiment has theadded advantage of allowing the user by means of the first timer 102 toselect the delay time between sequential operations of the solenoids 61,62 and 63. The user is also permitted through the second timer 103 toselect the “on” time, as shown from 0.5 to 5.0 seconds, for each of thesolenoids 61, 62 and 63 so that each filter 21, 22 and 23 will receiveone burst of backflushing ambient air for the selected backflush timeinterval. The time between solenoid operations is also set by thebackflush timer 103 and may be, but as shown is not, variable by theuser. As shown, an “off” time of 5 seconds is selected. This can be setat any value by the manufacturer. Assuming for example, an “off” time of0.5 seconds, the delay timer 102 being set for 3 minutes and thebackflush timer 103 being set for 10 seconds, the total cycle time willbe 3 minutes 45 seconds. That is, every 3 minutes and 45 seconds, eachfilter 21, 22 and 23 will be backflushed once.

As seen in FIG. 9, when power is applied, the delay timer 102 starts.The delay time can be set from 1.5 to 5 minutes by the operator with ascrew driver adjusted potentiometer 131 or some other type device. Whenthe delay timer 102 times out, it starts the backflush timer 103. Thesecond timer 103 operates the control relays 121, 122 and 123 whichactuate the switches 81, 82 and 83 to pick up the solenoids 61, 62 and63. Each solenoid 61, 62 and 63 is energized sequentially during thecycle. The duration “on” time for each solenoid 61, 62 and 63 isadjustable from 0.5 seconds to 5 seconds with an operator controlledscrew driver adjusted potentiometer 132 or some other device. Duration“on” time is the same for all solenoids 61, 62 and 63 once set. At theend of the cycle, the delay timer 102 is reinitiated. This cyclingcontinues until power is turned off. Preferably, the delay timer 102employs a single dual pressure monostable multi-vibrator 104 with avariable resistor 131 to permit delay time adjustment by the user. AnLED 106 is provided as confirmation of operation of the delay timer 102.The backflush timer 103 employs three such multi-vibrator chips 107, 108and 109 in a cascaded configuration with LED's 111, 112 and 113 and 114,115 and 116, respectively, to indicate the ON/OFF condition of each ofthe control relays 121, 122 and 123 which, in turn, pick up the switches81, 82 and 83 for their respective solenoids 61, 62 and 63.

A prototype of the ambient air backflushed filter vacuum wassatisfactorily tested with the following components: Element ComponentDescription 10 cannister 18¼″ I.D. × 22″ H 16 gauge carbonate steel 15vacuum 2-stage 110 volt AC 115 cfm vacuum motor source 19 plate 19¼″diameter 10-gauge galvanized cold rolled sheet metal 21, 22, 23 filters99.8% at 0.2 micron cartridge filters 25 cover 20″ diameter × 11″ H ABSplastic 34 valve 3″ diameter schedule 40 PVC plastic housings 35 ducts2″ diameter schedule 40 PVC plastic 36 ducts 1½″ diameter schedule 40PVC plastic 44 central 6″ diameter schedule 40 PVC plastic housing 48spacer 4″ diameter schedule 40 PVC plastic 61, 62, 63 solenoids 110 voltAC/pull rate of 4# at 0.5″ stroke 64 gaskets closed cell PVC foam 65valve plates 16 gauge cold rolled sheet metal 66 sleeves ¼″ diameter ×1¼″ aluminum spacers 67/68 bushing/bracket HMHD polypropylene/highimpact plastic 69 spring conical compression spring/1¾″ compressed to ¾″at 2.3 psi and fully compressed at 4 psi 85 cam motor 4 rpm geared ACmotor 104 multi-vibrator 555/4541 107, 108, multi-vibrator 4538 109

While the machine has been described in relation to a three filtersystem, the machine could employ any number of filters and associatedvalve, solenoid and switch combinations provided that at least two suchcombinations are employed so that at least one combination will alwaysprovide suction from the vacuum source 15. The valves 31, 32 and 33 mayemploy hinged covers or other mechanisms than pistons. The valveoperating mechanisms 31 d, 32 d and 33 d may be structurally differentas long as the vacuum ports “a” and ambient air ports “b” are closed atpressures not defeated by the suction of the vacuum source 15 but withinthe bias overcoming force of the solenoids 61, 62 and 63.

Thus, it is apparent that there has been provided, in accordance withthe invention, an ambient air backflushed filter vacuum that fullysatisfies the objects, aims and advantages set forth above. While theinvention has been described in conjunction with a specific embodimentthereof, it is evident that many alternatives, modifications andvariations will be apparent to those skilled in the art and in light ofthe foregoing description. Accordingly, it is intended to embrace allsuch alternatives, modifications and variations as fall within thespirit of the appended claims.

1. A vacuum cleaning machine comprising a cannister having an inlet portand at least two outlet ports, at least two filters disposed inside ofsaid cannister, one in pneumatic communication through a correspondingone of each of said outlet ports, a vacuum source, at least two valvesdisposed outside of said cannister, each said valve being in pneumaticcommunication between said vacuum source and a corresponding one of eachof said outlet ports and permitting air to be drawn by said vacuumsource from said inlet port simultaneously through corresponding ones ofsaid filters and means for sequentially operating said valves to switchsaid filters from connection to said vacuum source to connection toambient air and permitting ambient air to be intermittently drawnthrough corresponding ones of said valves and said filters into saidcannister.
 2. A vacuum cleaning machine according to claim 1 furthercomprising means cooperable with said inlet port to divide saidcannister into an upper zone of high velocity vortex air flow and alower zone of reduced velocity air flow.
 3. A vacuum cleaning machineaccording to claim 2, said inlet port being disposed below said filterand above a bottom of said cannister and said cooperable meanscomprising a duct directing air flow downwardly in said cannister fromsaid inlet port and a baffle redirecting said downward flow to acircumferential flow.
 4. A vacuum cleaning machine according to claim 1,said operating means having means for setting a cycle time of saidsequential valve operation.
 5. A vacuum cleaning machine according toclaim 1, said operating means having means for setting said intermittenttime of connection to ambient air for each said filter.
 6. A vacuumcleaning machine according to claim 1, said operating means having meansfor setting a cycle time of said sequential valve operation and meansfor setting said intermittent time of connection to ambient air for eachsaid filter.
 7. A vacuum cleaning machine according to claim 1, eachsaid valve comprising a housing having a continuously open port and tworeciprocally opened and closed ports therethrough, a piston reciprocallydisposed between said two ports and means biasing said piston tosimultaneously close one of said two ports and open another of said twoports.
 8. A vacuum cleaning machine according to claim 7, said operatingmeans further comprising means for overcoming said bias to move saidpiston to simultaneously open said one of said two ports and close saidanother of said two ports.
 9. A vacuum cleaning machine according toclaim 8, said bias overcoming means comprising at least two solenoids,one corresponding to each said valve, and means for energizing saidsolenoids to switch said valves to connect said filters to ambient airand for de-energizing said solenoids to switch said valves to connectsaid filters to said vacuum source.
 10. A vacuum cleaning machinecomprising a cannister having an inlet port and three outlet ports,three filters disposed inside of said cannister, one in pneumaticcommunication through a corresponding one of each of said outlet ports,a vacuum source, three valves disposed outside of said cannister, eachsaid valve being in pneumatic communication between said vacuum sourceand a corresponding one of each of said outlet ports and permitting airto be drawn by said vacuum source from said inlet port simultaneouslythrough corresponding ones of said filters and means for sequentiallyoperating said valves to switch said filters from connection to saidvacuum source to connection to ambient air whereby ambient air isintermittently drawn sequentially through corresponding ones of saidvalves and said filters into said cannister.
 11. A vacuum cleaningmachine according to claim 10 further comprising means cooperable withsaid inlet port to divide said cannister into an upper zone of highvelocity vortex air flow and a lower zone of reduced velocity air flow.12. A vacuum cleaning machine according to claim 11, said inlet portbeing disposed below said filter and above a bottom of said cannisterand said cooperable means comprising a duct directing air flowdownwardly in said cannister from said inlet port and a baffleredirecting said downward flow to a circumferential flow.
 13. A vacuumcleaning machine according to claim 10, said operating means havingmeans for setting a cycle time of said sequential valve operation.
 14. Avacuum cleaning machine according to claim 10, said operating meanshaving means for setting said intermittent time of connection to ambientair for each said filter.
 15. A vacuum cleaning machine according toclaim 10, said operating means having means for setting a cycle time ofsaid sequential valve operation and means for setting said intermittenttime of connection to ambient air for each said filter.
 16. A vacuumcleaning machine according to claim 10, each said valve comprising ahousing having a continuously open port and two reciprocally opened andclosed ports therethrough, a piston reciprocally disposed between saidtwo ports and means biasing said piston to simultaneously close one ofsaid two ports and open another of said two ports.
 17. A vacuum cleaningmachine according to claim 16, said operating means further comprisingmeans for overcoming said bias to move said piston to simultaneouslyopen said one of said two ports and close said another of said twoports.
 18. A vacuum cleaning machine according to claim 17, said biasovercoming means comprising at least two solenoids, one corresponding toeach said valve, and means for energizing said solenoids to switch saidvalves to connect said filters to ambient air and for de-energizing saidsolenoids to switch said valves to connect said filters to said vacuumsource.
 19. A vacuum cleaning machine comprising a cannister having anopening in a top thereof and an inlet port, a plate closing saidopening, said plate having three outlet ports, three filters mounted onsaid plate and disposed inside of said cannister, one in pneumaticcommunication through a corresponding one of each of said outlet ports,a vacuum source, three valves mounted on said plate and disposed outsideof said cannister, each said valve having a first port in continuouslyopen pneumatic communication with a corresponding one of said outletports, a second port in pneumatic communication with said vacuum sourceand a third port in pneumatic communication with a source of ambientair, a piston reciprocally disposed between said second and third ports,a coil spring biasing said piston to simultaneously close said thirdport and open said second port in a vacuum mode and a solenoid forovercoming said bias and reciprocating said piston to simultaneouslyclose said second port and open said third port in a backflush mode andmeans for operating said valves to sequentially switch said filter fromcommunication with said vacuum source to communication with ambient airfor a preset time.
 20. A vacuum cleaning machine according to claim 19,said operating means having means for setting a cycle time of saidsequential valve operation and means for setting an intermittent time ofconnection to ambient air for said filters.